Calculating device



Nov. 9, 1937.

E. C. WENTE CALCULATING DEVICE Filed Abril 10, 1935 2 Sheets-Sheet l F/GZ /NVENTOR E. C. WENTE Nov. 9, 1937.

E. C. WENTE CALCULATING DEVICE Filed April'lO, 1955 2 Sheets-Sheet 2 /NVENTOR B ECWENTE A T TORNEK Patented Nov. 9, 1937 i UNITED sTATEs PATENT OFFICE aosaszs t CALCULATING nevcn Edwin-110. Wentc, New York, N. Y., assignor to I Bell Telephone Lboratorie,

Incorporated,

New York, N. Y.. a comortion ot New York Application April 10, 1935, Serial No. 15,727 s Clalms. c. :s -1

This invention relates to calculating devices and particularly to devices i'or harmonic analysis.

The object of the invention is a devi'ce which wfll rapidly and accuratelydetermine the magnitude 5 and phase oi' the components o! the -Fourier series deiining a glvencurve. i

A feature of the invention is an electro-optical device !or multipying theordinates of the given curve by the ordinates oi' s, known modulatins function. r

Another feature of the invention is a device tor 'r rapidly varying the phase relation-between acompoflnt oi' the given curve and the modulating function.

13 Another feature of the invention is an electroi ;optical device for 'integrating the productoi' the 4 multiplication of the ordinates oi the given curve by the ordinates of the n'odulating function.

In the drawings: 4 .v Fig. 1 represents one cycle of the gives; curve;

Fig. 2 ditically shows a device enbodying the'invention;

Fig. 3 shows a modulating screen for the second v harmonic; and 4 Fig. 4 shows the image of the given 'curve superlmposed on the modulating screen.

In Fig. 1, one cycle of the given curve is represented as a transparency, having a transmison which varies in accor'dance with the given curve.

For convenience of illustration, this transparency function .Y= (Q) (l) in which the units oi abscissae; e, are so chosen that e has the values 0 and 21 at the two edges of the transparency. Let

h=the height o! the transmrency in centimeters 2-ra=the width of the transparency incentimeters,

If the transparency shown in Fig. l be uni- 5 formly illuminated by light of intensity I, the light transmitted by any vertical element having a width 'de will be i L= cIlTh r- 97 1 The curve represented 'by Equation 1 may also 5 be expressed by either oi' the Fourier series:

I! thelight transmitted through the flrst transparency, be transmitted through a second transparency having the coemcients of transmission !or light varying in the horizontal direction, the 25 light from any element of' the first transparency 'will be reduced in proportion. to the transmission of the aligned element of the second transparency. The light will thusbe doubly modulated and the tensty of the light transmitted through any so two aligned elements will be reduced in proportion to the product of the coemcients of transmission of the two elements. For convenienee of calculation, it is preferable that in one of the aligned transparencies, the transmission 'of an element should be uniform in the vertical direction even though the transmission of the various elements varies laterally. It is immaterial which transparency is so limited, thus, in the discussion' following the vertical elements of the 40 second transparency or modulating screen will be assumed to have'a coemcient of transmission for light which is constant in the vertical direction;

Let the transmission oi' the second transparency, or modulating screen, vary in the horizontal direction in accordance with the'follcwing relation.

r=n+r sin (nG-f-W) (5) Fig. 3 diagrammati'cally illustrates a moduleting screen in which the transmission of any vertical element is constant-'but the transmission of the various elements varies laterally in accordauee with Equation 5, when. 1=2; that is. the

From Equations 10, 11,12; 13, it !ollows that thus giving the coemcients of the sin'e and cosine terms of the Eourier series.

Fig. 2 diagrammatically. illustrates a device embodying the invention. The invention is not in any manner limited to the specific device illustrated in Fig. 2 and many modiflcations of .the device may obviously be made without departing from the spirit of the invention.

A transparency I hearing the given curve is uniformly illuminated by light from the source 2, condensed by the lens system 3. To obtain .niformity or illumination oi' the transparency i, the light so ce 2 may conveniently be a ribbon fllament r pointolite lampand the lens system 3 'may' project an image which is larger than the transparency I. A transparency 4 carries the modulating function o! Equation 5, of the proper order for. the desire'd harmonic. A lens system 5 projects an image oi'- the light from the transparency l on the transparency 4. The size oi' the image may be adjusted by known means, indicated by the screw I.

In Fig. 2, the transparency i is directly illuminated by the source-2, and produces an image on 'the modulating transparency 4. The positions of the transparencies may be interchanged so that the modulating transparency is directly illuminated and produces a'n image on the transparency i without changing the results so long as the beam of light is doubly modulated by both transparencies.

The transparency l may be shiited laterally by any suitable means, such as the micrometer screw 1. The doubly modulated light is collected by the lens system* 8 and in'pressed on the light sensitive device 9. The meter Io reads the output of the devices. A light proo! housing il encloses the various elements and prevents extraneous ight-from aflecting the device 9.

The transparency 4, lens 8 and photoeiectric,

cell 9 may be mounted on a iframe |2 which may be moved along the optical axis of the lens systems by a screw !3.

An image of the light source 2 is preferaby formed by the lens 3 on the lens 5. Under these circumstances, the interposition of the transparency l in the beam of light will not change the size of the image i'ormed at the lens 5, -but only the intensity of the light. Greater accuracy oi the measurements will be attained' by this adjustment. As the focus for this relationship is not particularly sharp, a small movement oi' the lens 5 will not destroy the relationship. Similarly, the lens 8 may form an image of the illuminated area of the lens 5 on the surface oi' 'the photoelectric cell 9. The interposition of the transparency 4 in the beam of light will not change the area of this image. but only the intensity of the light uniformly over the area, ot the image. Thua, the same area of the surface :of the photoelectric cell is illuminated at all times and the eflect of variations in the sensitivity o! the sur- 'ot the lens E Iormed on the surface oi' the photoelectric cell.

A modulating transparency I, of the proper.

order, is required for each harmonic to be determined. Thus, i'or the analysis o! a given curve to -the thirtieth harmonic, thirty modulating transparencies are required. These transparencies may be placed in order on a' flexible film, or, separate transparencies may be arranged on the periphery of a'rotatable drum and successively brought into the beam.

What is claimed is:

1. 'me method oi' which omprises preparing a transparency having a coeflicient of transmission varying laterally in accordance period -of the curv preparing a second transparency having a vertically 'constant coemcient analyzing a given curvev face is eliminated. The lens &should ,form an ;with the variations in one of transmission'varying laterally in accordance with a sinusoidal function having a period which is an p integral part of the period of the curve,

optically aligning both said transparencies in a uniform beam of radiant energy, detecting the total radiant energy transmitted through both transparencies, shirting said second trahsparency until the total radiant energy transmitted is a maximum, measuring said maximum, again shittirig said second transparency until the total radiant energy transmitted is a minimum, measuring said minimum, and determining the magnitude of a harmonic of said curve from said readings.

2. The method ot analyzing a given curve which comprises preparing a transparency having a coemcient of transmission varying laterally in accordance with the variations in one period of the curve, preparing sion varying laterally in accordance with a sinusoidal function integral part of the period of the curve, marking said second transparency .to indicates known value of said sinusoidal function, optically aligning both said transparencies in a uniform beam of radiant energy, detecting the total radiant energy transmitted through both transparencies, shifting said second transparency until the total 'radiant energy is a maximum, measuring the position of said mark with respect to the period oi' 'said curve, harmonic oi' said curve from said measurement;

3. The 'method of determining the coemcients of the sine terms of the Fourier series expressing the lateral variations in transmission oi' a transparency which comprises modulating a unii'orm beam oi' radiant energy in accordance with an integral number of cycles of said variations, successively modulating said beam in accordance a second transparency having a verticallyconstant coefllcient oi transmisand determining the phase oi' a having a period which is an r with a sinusoidal function having a period which V enemy !or each adiustment,

, n interalnumber ot cycles of `nci two right angles tions. measuring the with respect to said varie: doubly modulsted rediant and determinin the eine term !rom the diflerence of said mensurements.

4. The method o! determinin: the coemcients o! the cosine terms of the Fourier series expressin the lateral variations in transmission oi a. transparency which 'compries modultin e. unitorm beamrot radisnt energy in ccordnce with seid vritions, successively modulating seid besm in ccordance with a inusoidal !unction having a period which isaninteerlpertotperiodotsidvrltio sdiusting seid second modulation until the phase oi' seid second modultion is successively e right uncle. and three right anles with respect to said veritions, measuring the doubly modulet-,ed radint'enersy tor each odJustnent and determisaid first transparency muy ing the oosine term !rom the diiterence o! seid measurements.

5. A hermonic analyzer comprisin transperency vnryinz laternlly in trnnsmision in ccordance with n integral number ot cyclee `ot second trenprenc! hovin: 

